In some situations everybody around me use 重い, and when I went to the bicycle shop everyone was only using 重たい.
Both mean heavy, but what is the difference in meaning or context between them?
Can something be 重い but not 重たい? Or 重たい but not 重い?
重たい is supposed to be used when talking about personal opinions (subjective), while 重い is for general usage (objective).
But that said, when someone uses 重たい in a situation, another person may use the same word unintentionally because they are very similar.
Personally, I think 重たい has more feelings than 重い because you can stress the sound "たい", so it is like saying that you know how heavy it is by experience.
重たい
also holds a notion of "burden", which 重い
doesn't. That's why 腹に重たい食事
for example can't be used with 重い
, because it's not actually heavy it only feels like a burden. But other than that, either both can be used with the above nuances, or only 重い
works (e.g. in 身分が重い
or 口が重い
where there can't be any subjective notion of burden). One of these answers gives an extensive list.